In support of the needs of our clinical cardiac transplantation program, we have conducted experiments in dogs which indicate that the blood perfused, beating heart maintained ex vivo for 24 hours is immediately capable of sustaining the circulation following orthotopic transplantation. Since other investigators have claimed similar success using non-blood perfusion, we propose to compare the function of hearts preserved by each of these techniques to the function of acutely transplanted hearts and to acutely denervated, non-transplanted hearts. So that the pre-implantation status of the ex vivo donor heart can be evaluated, we will define the most practical functional and metabolic parameters of viability. These studies will also permit us to evaluate changes in function and metabolism with time so that the limits of ex vivo preservation might be determined and failure modes analyzed. To obtain maximum use of the experimental preparation, myocardial blood flow distribution and platelet distribution in the presence and absence of antiplatelet drugs will be determined. All functional results will be correlated with complete pathological evaluation. The completion of these studies, designed to support our ongoing clinical cardiac transplantation program, will result in a clinically useful device which will permit prolonged storage, distant transportation and critical functional evaluation of donor hearts. Although the ultimate goal is the development of a useful clinical tool, no human studies are included as a part of this grant application.